This is why the UC police didn’t stop the rioters: http://www.sfchronicle.com/bayarea/matier-ross/article/Why-UC-police-let-anarchists-run-wild-in-Berkeley-10908034.php
And as for the rioters, they are anarchists. That anarchists have a few characteristics that overlap with liberal left-wingers does not mean they deserve to be called “left-wing”. Doing so is just insinuating that there is direct or tacit support for their methods and actions by those who legitimately make up “the left” (liberals, progressives, Democrats, Greens, etc.). The common, perhaps defining, characteristic of those of us on the left is the belief in a central government. One that has strong regulatory powers, provides robust safety nets, healthcare (perhaps even someday here in the US), public education, funding for the arts and sciences, etc. Anarchists, do not.